This invention is directed to the ablation of tissue in the wall of a patient's heart and particularly to form channels within the heart wall in order to perform transmyocardial revascularization (TMR), to deliver therapeutic or diagnostic agents to various locations in the patient's heart wall or for a variety of other utilities.
As presently used, TMR involves forming a plurality of channels in a ventricular wall of a patient's heart by means of laser energy. The first clinical trials of the TMR procedure using laser energy were performed by Mirhoseini et al. See for example the discussions in Lasers in General Surgery (Williams & Wilkins; 1989), pp 18 216-223. Other early disclosures of the TMR procedure are found in an article by Okada et al. in Kobe J. Med. Sci 32, 151-161, October 1986 and in U.S. Pat. No. 4,658,817 (Hardy). These early references describe intraoperative TMR procedures which require an opening in the chest wall and include formation of channels completely through the heart wall starting from the epicardium.
U.S. Pat. No. 5,554,152 which issued on Dec. 20, 1994 (Aita et al.), which is incorporated herein in its entirety, describes a system for TMR which is introduced through the chest wall either as an intraoperative procedure where the chest is opened up or as a minimally invasive procedure where the system is introduced into the patient's chest cavity through small openings in the chest by means of a thoroscope. In U.S. Pat. No. 5,389,096 (Aita et al.) a percutaneous TMR procedure is described wherein an elongated flexible laser based optical fiber device is introduced through the patient's peripheral arterial system, e.g. the femoral artery, and advanced through the aorta until the distal end of the device extends into the patient's left ventricle. Within the left ventricle, the distal end of the optical fiber device is directed toward a desired location on the patient's endocardium and urged against the endocardial surface while a laser beam is emitted from its distal end to form the channel.
The laser based revascularization procedure has been shown to be clinically beneficial to a variety of patients, particularly patients who were, for the most part, not suitable candidates for by-pass surgery or for minimally invasive procedures such as angioplasty or atherectomy. However, to date the equipment for laser based systems has been quite expensive. What has been needed is a system which is cheaper than but as clinically effective as laser based systems. The present invention satisfies these and other needs.